1. Field of the Invention
The present invention generally relates to a semiconductor device having a capacitor component and a method for manufacturing the same. More particularly, the present invention relates to a semiconductor device having a capacitor component whose capacitance can be changed through changing the process, without changing the design, and a method for manufacturing the semiconductor device.
2. Description of Related Art
When two capacitor components having different capacitances are formed in a chip in a conventional semiconductor device, areas of capacitance electrodes for the two capacitor components are made different from one another.
More specifically, a first insulation film is formed on a silicon substrate and a polycrystal silicon film is deposited on the first insulation film. Then, a resist film is provided on the polycrystal silicon film, and the polycrystal silicon film is etched, using the resist film as a mask. As a result, first and second lower electrodes made of the polycrystal silicon film are formed on the first insulation film. Let us assume that areas of portions that become capacitance electrodes for the respective first and second lower electrodes are different from one another.
Then, impurities are ion-implanted in the first lower electrode and the second lower electrode with a predetermined dose. As a result, the impurity is introduced in the first lower electrode and the second lower electrode with the same impurity concentration. Then, a second insulation film (dielectric film) is formed on the first and the second lower electrodes. A polycrystal silicon film is deposited on the second insulation film. Then, a resist film is provided on the polycrystal silicon film, and the polycrystal silicon film is etched, using the resist film as a mask. As a result, a first upper electrode of the polycrystal silicon film is formed over the first lower electrode through the second insulation film, and a second upper electrode of the polycrystal silicon film is formed over the second lower electrode through the second insulation film. The semiconductor device is thus manufactured with the two capacitor components of different capacitances formed in one chip.
However, in the conventional semiconductor device described above, in order to form two capacitor components having different capacitances in one chip, areas of the lower electrodes are varied depending on the required capacitances. Therefore, when the capacitance of at least one of the two capacitor components is changed, the area of the lower electrode needs to be changed in the capacitor component whose capacitance is to be changed. In order to make such a change, a photomask that is used for patterning the lower electrode has to be redesigned and remanufactured. Consequently, a substantial cost is required to change the capacitances.
In accordance with one embodiment of the present invention, a semiconductor device includes a first capacitor component and a second capacitor component on a semiconductor substrate. The first capacitor component includes a first lower electrode formed from an impurity-doped polycrystal silicon film, a first insulation film formed on the first lower electrode and a first upper electrode formed on the first insulation film. The second capacitor component includes a second lower electrode formed from an impurity-doped polycrystal silicon film with an impurity concentration different from an impurity concentration of the impurity in the polycrystal silicon film of the first lower electrode, a second insulation film formed on the second lower electrode and a second upper electrode formed on the second insulation film.
In accordance with an additional embodiment, a first LOCOS oxide film is formed between the first capacitor component and the semiconductor substrate, and a second LOCOS oxide film is formed between the second capacitor component and the semiconductor substrate. In accordance with a further embodiment, an impurity is introduced into the first lower electrode and the second lower electrode by thermal diffusion.
In the semiconductor device embodiments described above, the amount of impurity introduced in the first lower electrode is different from the amount of impurity introduced in the second lower electrode, such that capacitances of the first capacitor component and the second capacitor component are different from one another. In the conventional semiconductor device, the area where the lower electrode and the upper electrode overlap each other has to be changed in order to change the capacitance of the capacitor component. However, in accordance with the present invention, the capacitance of the capacitor component can be changed by changing the amount of impurity that is introduced in the lower electrode, without changing the areas of the electrodes.
In the semiconductor device embodiments described above, from the viewpoint of design simplicity, the upper surface of the first lower electrode may preferably have the same area as that of the upper surface of the second lower electrode. Further, an impurity of a first dose may preferably be introduced in the first lower electrode, and an impurity of a second dose may preferably be introduced in the second lower electrode, by ion-implantation, respectively. Preferably, the first dose may be different from the second dose.
Also, from the viewpoint of dielectric strength characteristic, implementation of higher capacitance and stabilization of film quality, at least one of the first insulation film and the second insulation film may preferably be formed from an ONO film. The ONO film has a layered structure including an oxide film, a nitride film and an oxide film. Also, the first upper electrode and the second upper electrode may preferably be made of polycrystal silicon films.
Other features and advantages of the invention will be apparent from the following detailed description, taken in conjunction with the accompanying drawings that illustrate, by way of example, various features of embodiments of the invention.